Phonograph



Patented Feb. 26, 1946 UNITED' STATES PATENT oFFlcE PHONOGRAPH John J.Antalek, Chicago, Ill., assignor to Virgil Hamilton, doing business asHamilton Associated Industries, Chicago, Ill.

Application March s, 1942, serial No. 433,877

z claims. (ci. 17o-10011) This invention relates to a phonographor radiophonograph, and more particularly to the reproducing or amplifiercircuits of a phonograph, radio phonograph, or public address system.

It is an object of my invention to provide irnproved circuits for thereproduction of sound from phonograph records or the like.

A further object of the invention is to provide phonograph recordpick-up amplifying circuits having a high signal to noise ratio andimproved frequency response.

A more specific object of the invention is to Y provide improvedpick-up, reproducing, and amplifying circuits for phonograph recordplayers which shall obtain greater fidelity and quality in thereproduction of the phonograph signals.

A further and important object of the inven.. tion is to providephonographic and reproducing circuits wherein the phonographic pick-upcircircuit condenser 34 and the grid resistor 30 is grounded as at 40,andthereby connected to the plate circuit of the oscillator. Theselector switch 24 cooperates with the switch contact 22 and a likecontact 42 connected to the primary 46 of the usual antennacoupling-transformer 48, the secondary 50 of this transformer beingtunable by y the condenser 52, which is connected in shunt to thesecondary and connected by a wire 54 to the iirst radio receiver tube56, 'which may comprise a radio frequency amplifying tube, a' convertoror mixer tube or a detector tube.

The primary 46 is grounded as at 58 and the corresponding end of thesecondary is grounded as at 60. The tube 56 may comprise a plateelectrode 62, a screen grid electrode 64, a control grid 66, and acathode 68. The plate `electrode 62 is connected with a wire lll to theusual radio frequency or intermediate frequency output circuits 12 ofthe radio receiver, and in shunt thereto by a wire 14 through a resistor16 to a positive plate supply terminal 18, the negative side of the yplate -supply being, of course, grounded. The

screen grid electrode is connected by the wire 80 to the usual positivescreen grid supply terminal 82. The control grid is connected to thewire 54.

'The cathode 68 is connected to the cathode resistor 84, shunted by theby-pass condenser 86 and grounded as vat 88.

When the selector switch 24 is in position engaging contact 42, theradio receiver, of which the tube 56 constitutes the first tube,operates in phonograph circuit embodying the invention; and

Figure 2 is a. schematic diagram of another form of phonograph circuitembodying the invention.

In Figure 1 the phonograph circuit comprises an oscillator tube 2 havinga plate electrode 4, a control grid electrode 6, and a cathode 8. Theplate is connected by the wires I0 and I2 to the positive plate supplyterminal lI`4 through the resistor I6, the negative sideof the platesupply source being grounded. The plate is also connected through thewire l0, the wire i8, and the blocking condenser 2 0 to the contact. 22of s. selector swltch 24. The control grid 6 is connected by the wire26'to'a-grid condenser 28 and a grid resistor or leak 30, this condenserand resistor being connected in 'shunt to the' oscillator tank circuitcomprising an inductance coil 32 and a condenser 34, which may comprisea variable impedance phonographic pick-up. The cathode! `is connected bywire 36 to an intermediate point of the oscillator coil 32. Thc wire 38connecting the lower end 'of the oscillator coil to the tank the usualmanner to receive and reproduce radio signals. With this switch 24 inposition engaging contact 22, the radio receiver is disconnected fromthe antenna and thus made ineffective to receive or reproduce radiosignals, but is connected to the phonographic circuit. vWith the switchin this position, the antenna transformer 48 is tuned by the condenser52 to a frequency within approximately plus and minus eight kilocyclesof the unmodulated signal carrier supplied by the oscillator, of whichthe tube 2 vforms a` part. Variations in the impedance of the pick-up,due

to the lateral undulations of the record groove.

effect a frequency modulation of the carrier or the signal supplied bythe oscillator. This frequency modulated signal is transmitted as anamplitudel modulated signal by the tuned antenna coupling to the inputcircuit of the tube 56, which amplifles or converts the 'signal andpasses it to the R. F. or I. F. output circuit 12 of the receiver. Itwill be understood that the remaining usual circuits of the radioreceiver ampliiiesgthe modulated signal supplied to the output circuit12, and/or convert it into I. F. amplitude modulated signal which isthen detected, amplied and supplied to the reproducer or loud speaker.

In the case of a tuned radio frequency receiver, the'tube'56 mayconstitute a radio frequency amplifier feeding into the usual circuits,Where the phonographically modulated signal is detected, amplified, andsupplied to the reproducer or loud speaker. In the case of a'superheterodyne receiver, the tube 56 or the electrodes thereof mayalso constitute a part of the convertor or mixer section, by which themodulated Vsignal or radio frequency is converted into va modulatedintermediate frequency signal, and' thereafter ampliiied and convertedinto audio frevcondenser being connected in series with the resistor inthis shunt circuit so as' to vary the effective impedance and theresultant frequency of the oscillator circuit in accordance with theundulations of the record groove. Where an impedance pick-up isemployed, it may be connected so as to form all, or a part, of thetankcircuit inductance 92.

In the circuit shown in Figure 2, an oscillator tube or tube section 90is connected to a detector tube or section 92 by' a doubly tunedtransformer coupling 94. The oscillator tube or section ,90 comprises4 aplate 96, a control grid 98, and a cathode |00. The cathode is connectedby the wire |,02 to an intermediate point of the adjustable tank circuitinductance coil |04. The control grid is connected by a wire |06 to oneside pacity type pick-up ||2 grounded as at H4. It

will, of course, be evident that the phonographic pick-up may be of aresistance or inductance type so connected as to eifect a frequencymodulation of the carrier or unmodulated signal supplied by theoscillator. Where a resistor or inductance type of pick-up is employed,the capacity necessary for the tank circuit of the oscillator may beprovided by a condenser connected-in the saine manner as the pick-upcapacity 2; withthis condenser, in the case of a resistor pickup,"beingshunted by the pick-up and an auxiliary condenser connected in/serieswith the pick-up resistor. In the case of the inductance type pickup,the pick-up may form apart or all of the tank circuit coil |04.

The plate electrode 96 is connected by a wire ||6`to one side of theprimary winding ||9 of. the transformer coupling v94,'the-other side vof,the primary being connected'by a wire |20 to the positive plate supplyterminal |22. The pri- .mary ||8 is tunable by a condenser |24 in shunttherewith,

'I'he detector tube or section 92.,may comprise-a plate ,electrode |26,-a control grid |28, and a` cathode |30. The Icontrol grid is connectedthrough grid condenser |32 and bywire |34 to one side of the secondarywinding |36 of the aseaseo' transformer coupling 94. @The other side ofthe secondary winding f 36 is grounded by the wire |38. The secondarywinding is shunted by tuning condenser I 4ll.l The cathode I 30 isconnected to the ungrounded end of the cathode biasing resistor |42which is shunted by the usual bypass condenser |44 and groundedvas at|46. The control grid is connected to the grounded end of the biasingresistor through the grid resistor o r leak |48. l

The plate electrode |26 is connected by a wire |50 to the ungroundedside of an R. F. by-pass condenser |52; to the positive plate supplyterminal |54 through a resistor |56; and to audio output circuit |58through blocking condenser |60. I'he audio output circuit |58 maycomprise any usual audio amplifier or audio amplifying section of aradio receiver orpublic address system, by which the audio signals inthe output circuit of the detector tube or section 92 are amplined andsupplied to the usualreproducer or loud speaker.

'I'he oscillator and detector sections 90 and 92 graphic pick-up alongthe steep slope of the selectivity curve ofthe doubly tuned transformercoupling 94. Accordingly, this coupling impresses on the input circuitof the. detector tube a radio frequency amplitude modulated signal, andthis signal is detected by the-detector tube'or section and supplied tothe audio output circuit. r It is thought that the inventionand numerousof its attendant advantages will be understood from the foregoingdescription, and it is'obvious that numerous changes may be made in theform,

construction and arrangement 'of the several parts without departingfrom the spirit or scope ant advantages, the formshherein describedbeing preferred embodiments for thepurpose of illustratingthe invention.

Having thus described my invention, what claim as new and desire tosecure by Letters Patent is:

1. In a radio phonograph, a radio receiver comprising aiirstir'adiofrequencyamplifier, and a tuned antenna coupling in the input of saidampllfler, a phonographic circuit adapted to be connected to saidantenna coupling circuit, saidl phonographic circuit comprising animpedance varying record pick-up, an oscillator having plate, grid, andcathode electrodes, means for connecting said antenna couplingcircuit'in the plate-tocathode circuit of said tube.' and a tank circuitconnected to all of said electrodes forgenerating radio frequencyoscillations, said tank circuit having inductive and capacitivebranches, one of said branches including said pick-up to tune saidoscillator and vary the frequency of oscillations-in said antennacoupling circuit, said tuned antenna tuning said circuit to afrequencywithin the side bands of the modulated oscillations supplied toof the invention or sacrificing any of its attendcoupling circuitincluding a, tuning element fox" said antenna ccuplins circuit by saidPhcn0 i l0 graphic circuit.

coil connected tuali ofsaid electrodes,r said ca-v pacity Avaryingpick-up being connected in shunt to said coil to tune said phonographiccircuit and vary the` frequency of the oscillations supplied to saidantenna coupling circuit, said tuned antenna coupling circuit includinga tuning element for tuning said circuit t0 a frequency within the sidebands of the modulated oscillations supplied to said antenna couplingcircuit by said phono- I i JOHN J.

